Newts are classified under the phylum, Chordata. Chordates are organisms that possess a dorsal hollow nerve chord, a tail thatextends beyond the anus, and notochord. A notochord is a dorsal supporting rod composed of a core of large cells with turgid fluid filled vacuoles, which make it rigid but flexible. In newts, the notochord is replaced by the jointed, dorsal vertebral column, which replaces the notochord as the primary supporting structure early in development. Thus, newts are further classified as vertebrates, a subphylum of chordata.
Some characteristics of vertebrates are:
An anterior skull that houses a brain
A rigid internal skeleton supported by the vertebral column
Internal organs suspended in coelom
A well developed circulatory system driven by contractions of a ventral heart
Newts are amphibians. Amphibians are cold blooded, meaning they cannot regulate their own body temperatures. Most undergo metamorphosis from a juvenile state to an adult state, and they spend at least part of their life on both water and land (13).
Newts are a specific type of amphibians called salamanders. Salamanders have four legs, a slender body, and a tail.
Habitat and Niche
In general, salamanders prefer cool, shady environments. Salamanders are most prevalent in the temperate regions of the Northern Hemisphere, specifically in deciduous or coniferous forests, but many types are also found in cool, moist environments in the mountains of Central America or the South American tropics. All species of salamander are aquatic or semi-aquatic. Many salamanders live in rotting logs or moist soil (14).
Predator Avoidance
Many newts protect themselves from predators by secreting highly potent toxins from paratoid glands on their skin. These toxins can make the newts inedible or even deadly to predators that attempt to eat them. Newts are capable of producing neurotoxins such as tetradotoxin that block the nerve signals to muscles of these predators, which can stop their heart and lungs from functioning. (6) However, some predators, such as some genetic variants of garter snakes, have evolved a resistance to this toxin. This provides a classic example of coevolution and the evolutionary arms race. (8)
Newts also rely on certain skin colors to deter predators. Some newts have brown, black, or green skin to blend in with the surrounding environment and camouflage the newt. Other times, newts that use toxins may also have brightly colored (often red or orange) skin to warn predators of their toxicity and show that that they are undesirable prey. (6) (7)
Sensing the Environment
Newts are unable to hear sound; however, they can feel the sound’s vibrations in the ground and react. To make up for their lack of hearing, newts have well developed sight and smell senses (8).
Movement
Newts have short, little legs and when they are on land, they support their bodies as they walk by bending from side to side. The tails are used for support as well and they help newts move their in an s-shape in water. These strategies also help newts move quickly when they need to escape from predators (1).
Waste Removal
Newts have a normal waste removal system, in which nutrients are taken in through the mouth and excreted through the rectum as feces. As nitrogenous waste builds up in the blood, the liver produces urea which is then processed by the kidneys then excreted out of the body.
Circulation
Newts have three-chambered hearts, which consist of two atria and a single ventricle, that connects to two loops that connect to the lungs and the rest of the body. The right atrium receives the deoxygenated blood as the left recieves the oxygenated blood, but the two mix in the single ventricle, reducing efficiency because both types are sent to the body and lungs. In order to live on land, newts require more oxygen, and therefore have developed lungs and become amphibious (2) This diagram shows how the three-chambered heart of the newt (middle) compares to the hearts of other vertebrates.
Gas Exchange
Newts, and essentially all amphibians, have moist and highly vascularized skin, so they can exchange gas through their skin and mouth lining. Most newts also possess lungs. While a newt is a tadpole, it has gills to get oxygen, but as an adult it has lungs to breath oxygen. The lungs of newts have large alveoli, so the lungs do not exchange gas as efficiently as do the lungs of more complex organisms such as mammals (15).
Nutrient Acquisition
Newts are carnivores. Aquatic newts larvae feed on small invertebrates, such as beetle larvae and snails. Adult Newts feed on macro invertebrates, and small aquatic larvae such as midge larvae (10). Newts locate prey by sight or smell then lunge at the prey while extending their sticky tongue to ensnare their prey (16).
Environmental Physiology
As amphibians, newts cannot regulate their temperature metabolically. Salamanders must find shade to avoid overheating or find warmer areas to prevent becoming too cold. However, salamanders have moist skin, which can act as an evaporative cooling system. As a result, most salamanders can only live warm, moist environments (11).
Chemical Control/Endocrinology
Salamander limb regeneration is still being studied, but research has shown the various hormones that are important for proper limb regeneration. Insulin, growth hormone, hydrocortisone, and thyroxin are some of the hormones necessary for optimum limb growth and cartilage differentiation. No single hormone has the ability to support limb regeneration because it is a multi-hormone process.
Integument
Newts have smooth skin and lack scales or hair. The skin is moist because respiration occurs through the skin. Some newts have poisonous glands on their skin which helps protect against predators. (9)
Reproduction
Salamanders reproduce through internal fertilization, which is achieved through the transfer of a small sperm embedded capsule called a spermatophore. Males attract females with loud, species-specific calls and compete for females at breeding sites. Many amphibians lay large numbers of eggs which they abandon once they are deposited. Other amphibians lay few eggs which they guard. A few species of salamanders are viviparous, meaning they give birth to well developed young that receive nutrition from the mother during gestation.
Growth and Development
(5)
2 to 3 weeks after newt eggs are laid, they hatch into tadpoles, which for a few days live off the food reserves contained within their yolk sacs. Then they start to eat freshwater plankton, and later insect larvae and mollusks. The larvae have external gills, which absorb oxygen directly from the water. About 10 weeks later they have metamorphosed into air-breathing juveniles, known as "efts." They become sexually mature at 3 years of age. The average life span of a newt is 6 years. (3)
Relationship to Humans
Newts are able to regrow limbs, and scientists are studying the connection between the cells that rapidly reproduce to regrow limbs and human cells that reproduce and form cancerous tumors. Scientists have found that the chemicals made in a newts body during regrowth are the same chemicals that cause cancer in other animals. Further studies on this connection may lead to more effective cancer treatments for humans (12).
Review Questions:
1. How are newts able to use their strong sense of the environment (minus sound) to avoid predators?
2. How do the circulatory pathways of newts differ from humans and from fish?
Table of Contents
Classification
Kingdom: Animalia
Phylum: Chordata
Class: Lissamphibia
Order: Caudata/Urodela
Family: Salamandridae
Newts are classified under the phylum, Chordata. Chordates are organisms that possess a dorsal hollow nerve chord, a tail thatextends beyond the anus, and notochord. A notochord is a dorsal supporting rod composed of a core of large cells with turgid fluid filled vacuoles, which make it rigid but flexible. In newts, the notochord is replaced by the jointed, dorsal vertebral column, which replaces the notochord as the primary supporting structure early in development. Thus, newts are further classified as vertebrates, a subphylum of chordata.
Some characteristics of vertebrates are:
Newts are amphibians. Amphibians are cold blooded, meaning they cannot regulate their own body temperatures. Most undergo metamorphosis from a juvenile state to an adult state, and they spend at least part of their life on both water and land (13).
Newts are a specific type of amphibians called salamanders. Salamanders have four legs, a slender body, and a tail.
Habitat and Niche
In general, salamanders prefer cool, shady environments. Salamanders are most prevalent in the temperate regions of the Northern Hemisphere, specifically in deciduous or coniferous forests, but many types are also found in cool, moist environments in the mountains of Central America or the South American tropics. All species of salamander are aquatic or semi-aquatic. Many salamanders live in rotting logs or moist soil (14).
Predator Avoidance
Many newts protect themselves from predators by secreting highly potent toxins from paratoid glands on their skin. These toxins can make the newts inedible or even deadly to predators that attempt to eat them. Newts are capable of producing neurotoxins such as tetradotoxin that block the nerve signals to muscles of these predators, which can stop their heart and lungs from functioning. (6) However, some predators, such as some genetic variants of garter snakes, have evolved a resistance to this toxin. This provides a classic example of coevolution and the evolutionary arms race. (8)Newts also rely on certain skin colors to deter predators. Some newts have brown, black, or green skin to blend in with the surrounding environment and camouflage the newt. Other times, newts that use toxins may also have brightly colored (often red or orange) skin to warn predators of their toxicity and show that that they are undesirable prey. (6)
Sensing the Environment
Newts are unable to hear sound; however, they can feel the sound’s vibrations in the ground and react. To make up for their lack of hearing, newts have well developed sight and smell senses (8).Movement
Newts have short, little legs and when they are on land, they support their bodies as they walk by bending from side to side. The tails are used for support as well and they help newts move their in an s-shape in water. These strategies also help newts move quickly when they need to escape from predators (1).Waste Removal
Newts have a normal waste removal system, in which nutrients are taken in through the mouth and excreted through the rectum as feces. As nitrogenous waste builds up in the blood, the liver produces urea which is then processed by the kidneys then excreted out of the body.Circulation
Newts have three-chambered hearts, which consist of two atria and a single ventricle, that connects to two loops that connect to the lungs and the rest of the body. The right atrium receives the deoxygenated blood as the left recieves the oxygenated blood, but the two mix in the single ventricle, reducing efficiency because both types are sent to the body and lungs. In order to live on land, newts require more oxygen, and therefore have developed lungs and become amphibious (2)This diagram shows how the three-chambered heart of the newt (middle) compares to the hearts of other vertebrates.
Gas Exchange
Newts, and essentially all amphibians, have moist and highly vascularized skin, so they can exchange gas through their skin and mouth lining. Most newts also possess lungs. While a newt is a tadpole, it has gills to get oxygen, but as an adult it has lungs to breath oxygen. The lungs of newts have large alveoli, so the lungs do not exchange gas as efficiently as do the lungs of more complex organisms such as mammals (15).Nutrient Acquisition
Newts are carnivores. Aquatic newts larvae feed on small invertebrates, such as beetle larvae and snails. Adult Newts feed on macro invertebrates, and small aquatic larvae such as midge larvae (10). Newts locate prey by sight or smell then lunge at the prey while extending their sticky tongue to ensnare their prey (16).Environmental Physiology
As amphibians, newts cannot regulate their temperature metabolically. Salamanders must find shade to avoid overheating or find warmer areas to prevent becoming too cold. However, salamanders have moist skin, which can act as an evaporative cooling system. As a result, most salamanders can only live warm, moist environments (11).Chemical Control/Endocrinology
Salamander limb regeneration is still being studied, but research has shown the various hormones that are important for proper limb regeneration. Insulin, growth hormone, hydrocortisone, and thyroxin are some of the hormones necessary for optimum limb growth and cartilage differentiation. No single hormone has the ability to support limb regeneration because it is a multi-hormone process.Integument
Newts have smooth skin and lack scales or hair. The skin is moist because respiration occurs through the skin. Some newts have poisonous glands on their skin which helps protect against predators. (9)Reproduction
Salamanders reproduce through internal fertilization, which is achieved through the transfer of a small sperm embedded capsule called a spermatophore.Males attract females with loud, species-specific calls and compete for females at breeding sites.
Many amphibians lay large numbers of eggs which they abandon once they are deposited. Other amphibians lay few eggs which they guard. A few species of salamanders are viviparous, meaning they give birth to well developed young that receive nutrition from the mother during gestation.
Growth and Development
2 to 3 weeks after newt eggs are laid, they hatch into tadpoles, which for a few days live off the food reserves contained within their yolk sacs. Then they start to eat freshwater plankton, and later insect larvae and mollusks. The larvae have external gills, which absorb oxygen directly from the water. About 10 weeks later they have metamorphosed into air-breathing juveniles, known as "efts." They become sexually mature at 3 years of age. The average life span of a newt is 6 years. (3)
Relationship to Humans
Newts are able to regrow limbs, and scientists are studying the connection between the cells that rapidly reproduce to regrow limbs and human cells that reproduce and form cancerous tumors. Scientists have found that the chemicals made in a newts body during regrowth are the same chemicals that cause cancer in other animals. Further studies on this connection may lead to more effective cancer treatments for humans (12).Review Questions:
1. How are newts able to use their strong sense of the environment (minus sound) to avoid predators?2. How do the circulatory pathways of newts differ from humans and from fish?
References:
1. http://animal.discovery.com/amphibians/newt-info.htm
2. http://www.biologyjunction.com/amphibian_notes_bi.htm
3. http://www.animalcorner.co.uk/britishwildlife/commnewt.html
4.http://www.axolotl.org/biology.htm
5.http://www.sentinelsource.com/parent_express/resources/the-joy-of-the-unexpected-encounter/article_8a810386-879c-11e0-a2c9-001cc4c002e0.html?mode=image&photo=0
6. http://www.caudata.org/cc/articles/toxin2.shtml
7. http://ih2.redbubble.net/image.11352126.8443/flat,550x550,075,f.jpg
8. http://www6.montgomerycountymd.gov/dectmpl.asp?url=/Content/dep/water/monBioNewts.asp
9. http://animals.about.com/od/newtssalamanders/p/newtssalamanders.htm
10. https://academics.skidmore.edu/wikis/NorthWoods/index.php/Notophthalmus_viridescens_-_Red_Spotted_Newt
11. http://sparknotes4pak.blogspot.com/2012/06/temperature-regulation-in-amphibians.html
12. http://science.howstuffworks.com/zoology/reptiles-amphibians/salamander-regrow-body-parts1.htm
13. http://www.nwf.org/wildlife/wildlife-library/amphibians-reptiles-and-fish.aspx
14. http://a-z-animals.com/animals/salamander/
15. https://www.boundless.com/biology/respiratory-system-and-gas-exchange/breathing-aerates-the-lungs/breathing-in-amphibians/
16. http://www.britannica.com/EBchecked/topic/21445/amphibian/40624/Food-and-feeding